It has heretofore been proposed to provide oxygen masks which form a cup like, enclosure over the nose of the patient so that apertures in an oxygen supply tube will discharge oxygen into the enclosed chamber of the mask for inhaling by the patient.
Exemplary of such devices are the masks disclosed in the following patents:
U.S. Pat. No. 1,288,647, Miller; Dec. 21, 1918 PA1 U.S. Pat. No. 1,632,449, McKesson; June 14, 1927 PA1 U.S. Pat. No. 2,843,121, Hudson; July 15, 1958 PA1 U.S. Pat. No. 2,843,122, Hudson; July 15, 1958 PA1 U.S. Pat. No. 2,859,748, Hudson; Nov. 11, 1958 PA1 U.S. Pat. No. 3,889,671, Baker; June 17, 1975 PA1 U.S. Pat. No. 4,354,488, Bartos; Oct. 19, 1982
The enclosed chambers of these masks, usually have one way air outlet valves in a side, or bottom wall but they tend to build up heat, fear of asphyxiation and possibly can cause suffocation due to vomitting.
In U.S. Pat. No. 4,263,908 to Mizerak of Apr. 28, 1981 a nasal cannula mask is disclosed which has an enclosed chamber fitting over the mouth and is supported on the chin of the wearer.
Another known device for administering oxygen is marketed as "The Face Shield" by Hudson Oxygen Therapy Sales Co. of Temecula, Calif. It does not have an enclosed cup-like chamber, but instead is an open bottom skirt which extends from the bridge of the nose down to the level of the bottom of the chin with apertures in the front wall facing upwardly and rearwardly from the level of the lower lip toward the nostrils. This device is of such large area that fixation without leakage to the eyes presents problems, especially if the patient rolls over, or the lower tip of the mask is inadvertently struck. Fixation is by elastic straps over the ears and a strip of moldable metal which is intended to be molded by the fingers to fit over the bridge of the nose.
The Bartos nose mask of U.S. Pat. No. 4,354,488, discloses a shell with a gas delivery tube having gas delivery openings within the shell directed in any of a variety of directions usually toward the mouth or nose. It also teaches that the gas delivery tube should be below the tip of the wearers nose, and not under the nostrils, so that the area under the nose is completely open.